MATE 1.6 was committed to FreeBSD ports on 23 November 2013. Get it there.
MATE is a fork of GNOME 2. More information can be found at http://mate-desktop.org/. This is a place where you can get MATE ports development for FreeBSD. When the MATE ports are stable and it will be merged into FreeBSD ports tree.
You will need to make sure you have latest ports tree before you grab MATE. I am not going to give you a baby step of how to update FreeBSD ports tree or install other apps if your command line doesn't work. The FreeBSD Handbook (http://www.freebsd.org/) is a place where you need to visit and read. You will need to install the devel/git as matemerge.sh depends on it to fetch mate-ports from GitHub. Anyway, let's get start to grab matemerge.sh script that will allow merge the mate-ports into your /usr/ports.
# fetch http://people.freebsd.org/~mezz/script/matemerge.sh
You will need to edit in the marcusmerge in your editor. The two variables, SRCDIR and DESTDIR are what you need to change it. You may skip DESTDIR if it's same default in your FreeBSD. To merge mate-ports into FreeBSD ports:
# sh matemerge.sh
There are two different choices of mate ports, x11/mate-base or x11/mate, to install MATE desktop. The x11/mate-base is a bare desktop without any of extra MATE applications such as editor, terminal, calculator and other. It only has file manager and panel. The x11/mate is a full desktop with editor, terminal, calculator and other applications.
It is recommend to unmerge the mate-ports first before you update your FreeBSD ports tree.
# sh ./matemerge.sh -U
After that, update your ports tree by either svn, portsnap or other methods then use the matemerge.sh to update it.
# sh ./matemerge.sh -u
Please see the TODO-mate file.